Vacuum tube and method of constructing the same



Patented Jan. 31, 1928.

UNITED STATES PATENT OFFICE.

HERBERT E. METCALF, OF SAN LEANDRO, CALIFORNIA, ASSIGNOR TO THE MAGNA- VOX COMPANY, OF OAKLAND, CALIFORNIA, A CORPORATION OF ARIZONA.

VACUUM TUBE AND METHOD NoDrawing.

This invention relates to vacuum tubes such as are ordinarily used for rectifying and amplifying purposes, and as electric Wave generators. 1

5 It is well known in the manufacture of vacuum tubes that certain substances which are commonly known as getters may be vaporized inside the vessel either durin or after evacuation. This vaporization aids in clearing up residual gases left in the vessel,

by chemical combination, physical absorption, or by blanketing or enclosing gas molecules.

Such substances as are commonly in use include chemicals such as red phosphorus, metals such as magnesium, or a comblnation of several.

It is the usual procedure to insert such getters either as a coating on the various electrodes of the evacuated vessels, or'in the case of metals, to afix them by welding, or

some similar method, and vaporizing them by means of heat.

It is also well known in the art that these etters have a selective clean-u eflect;

that is, certain metals or substances being able to clean up, absorb,.or otherwise rid the vessel of a certain gas, others of another gas.

Heretofore all such substances have either been inserted into the vessel as an element or attached to an electrode. However, I have found a new and useful method of obtaining the same results by the use of an electrode formed of the material known to the trade as German silver. German silver is an alloy of zinc, copper, and nickel. In the present invention I provide an evacuated vessel having contained therein one or more electrodes composed of commercial German silver.

.The vacuum tube is constructed with the desired number of electrodes, according to the purpose it is to serve. One or more of these electrodes, preferably the cold anode or the so-called grid or control electrode, or

both, isformed of German silver.

Upon heating one or more of vthe electrodes of my device by any of the many ways well known in the art, during evacuation a dissociation of the German silver Application filed July 23,

\parts showing the silvery zinc color.

OF CONSTRUCTTNG THE SAME.

1924. Serial No. 727,707.

takes place, whereby part of the copper and part ofthe zinc distills oil at certain temperatures, and is deposited on the walls of the tube in the form of a film. The nickel remains behind, and the mechanical strength 5:; of the electrode is unimpaired.

The film of copper and zinc which is dissociatedfrom the German silver acts as a selective getter as it cools. The' vessel is sealed while this film is still hot, and the absorption of the desired gases raises the vacuum after sealing.

It is of interest to note that in my method the copper and zinc are deposited separately on the walls of the vessel, parts of which show a bright copper-red sheen, and other In certain parts of the vessel, however, the copper and zinc seem to re-alloy, and have the characteristic luster of brass.

It is evident from the high clean-up of gases after sealing that several different gases are absorbed; just which ones I am not yet preparedto state. I do know, however, that this method gives a strong, effective clean-up, suflicient to give proper operation of a hot cathodecold anode device, even when an indifferent vacuum is present at the moment of sealing.

What I claim as new and desire to secure so by Letters Patent is:

- 1. A method of constructing a vacuum tube which consists of forming one of the electrodes of German silver and heating said electrode to throw off the copper and S5 zinc component of the German silver and depositing the same upon the walls of the tube, the remaining constituents of the German silver, principally nickel, being left in place to form an electrode.

2. A three-electrode vacuum tube composed of a hot cathode, a control electrode and an anode, one of the electrodes being composed of commercial German silver which has been heated to the point where 95 copper and zinc are deposited on the walls of the tube before sealing, and the nickel is left in place to form an electrode.

HERBERT -E. METCALF. 

